Yamamoto Rock Machine (Former Yamamoto Iron Works) Former Research Laboratory Building

Yamamoto Rock Machine Former Research Laboratory: Where Japanese Rock Drills Began

The Yamamoto Rock Machine (Former Yamamoto Iron Works) Former Research Laboratory Building (ヤマモトロックマシン（旧山本鉄工所）旧研究室棟) is a single-story timber laboratory built in the early Showa period (1926 to 1945) behind the company's old head office in Tojo-cho, Shobara City, Hiroshima Prefecture, and it was entered on the national register as a Registered Tangible Cultural Property on 3 December 2024. It covers just 131 square meters, a fraction of the size of the factories nearby, yet the Agency for Cultural Affairs singles it out as the building where the company's rock drill manufacturing started.

It looks Western at first glance. A tiled gable roof runs east to west with the entrance on the long side, and the walls are lined with tall windows whose heads close in semicircular arches. The walls are finished in scraped mortar, a stucco technique that leaves a fine, gritty texture. Japanese roof tiles over arched windows set in pale, rough walls: behind the townhouses of Tojo, the outline is unlike anything else on the street.

The official record dates the building to the prewar Showa years and notes a renovation in 2023, completed shortly before the registration.

Why the Former Research Laboratory Was Registered

Ten buildings at Yamamoto Rock Machine are on the register, and nine of them were listed for contributing to the historic landscape. The former research laboratory is the exception. It was registered under a different criterion, as a model of design, meaning that the form of the building itself was judged worth keeping, not only its place in the townscape.

The arched windows and scraped-mortar walls carry that judgment. A provincial manufacturer in the 1930s chose a Western vocabulary for a building meant for testing and design work, and set it on a plain tiled single-story frame without strain. The former head office on the street front, registered on the same day, has the same scraped-mortar finish, so the public office and the private laboratory behind it were clearly meant to match.

The other value lies in what happened inside. The company grew out of repairing imported rock drills for dam builders, went on to make its own, and says it brought in an engineer from Germany to learn heat treatment. When the Agency calls this building the starting point of rock drill manufacturing, it points to the stage before mass production: prototypes, measurement and trial and error. Among the ten Yamamoto Rock Machine buildings, this one carries the most weight in the firm's story.

What to Look For at the Research Laboratory

Start with the windows. Tall openings topped with half-round arches march along the sides at an even rhythm. Against the grainy wall surface the curves stand out cleanly, and they play well against the long horizontal line of the tiled eaves.

The plan is simple and a little unusual. A wooden-floored laboratory room fills the center, with an earth-floored passage along its north side and another along its south side. The laboratory opens onto both passages with doors and windows, so daylight from the arched outer windows reaches the room by way of the corridors. One way to read the arrangement is as a split between passages where parts and tools could be carried in with shoes on, and a raised timber floor for the slower work of measuring and testing.

The Agency's record photographs show the west face seen from the southwest across a courtyard, and the entrance to the north passage. If you ever get close, those are the two views to seek out: the arcade of windows seen obliquely from the southwest, and the step up from the earthen passage at the doorway.

Visiting the Former Research Laboratory

The Yamamoto Rock Machine research laboratory stands on company land and is not open on a regular basis. It sits directly east of the old head office, which faces west onto Shinmachi-suji, so from the street the office block hides most of it.

The interior can be seen only during open days or events run by the company or the local preservation group. Do not enter the grounds without permission, and keep photography to the public road. Since the building was renovated in 2023, an announced open day is also the chance to see how the refurbished rooms are used today.